👤 Nuno Cardim

Hypertrophic cardiomyopathy (HCM) is a genetically and phenotypically heterogeneous disease; there is still a large proportion of patients with no identified disease-causing mutation. Although the majority of mutations are found in the MYH7 and MYBPC3 genes, mutations in Z-disk-associated proteins have also been linked to HCM. We assessed a small family with HCM based on family history, physical examination, 12-lead ECG, echocardiogram and magnetic resonance imaging. After exclusion of mutations in eleven HCM disease genes, we performed direct sequencing of the TCAP gene encoding the Z-disk protein titin-cap (also known as telethonin). We present a novel TCAP mutation in a small family affected by HCM. The identified p.C57W mutation showed a very low population frequency, as well as high conservation across species. All of the bioinformatic prediction tools used considered this mutation to be damaging/deleterious. Family members were screened for this new mutation and a co-segregation pattern was detected. Both affected members of this family presented with late-onset HCM, moderate asymmetric left ventricular hypertrophy, atrial fibrillation and heart failure with preserved ejection fraction and low risk of sudden cardiac death. We present evidence supporting the classification of the TCAP p.C57W mutation, encoding the Z-disk protein titin-cap/telethonin as a new likely pathogenic variant of hypertrophic cardiomyopathy, with a specific phenotype in the family under analysis. Show less

We present an ancillary study of the Portuguese Registry of Hypertrophic Cardiomyopathy (PRo-HCM). This is one of the largest HCM genetic studies based on a registry. Collected genetic variants were re-analysed for pathogenicity. Demographic, clinical, imaging and outcome data were analysed for associations with genotype, focusing on comparisons between patients with (G+) vs without (G-) a pathogenic/likely pathogenic (P/LP) variant in one the 9 main causal sarcomeric genes. From the 1042 patients in the registry, 528 (51%) had genetic testing. 152 (28%) were G+ and 98 pts. (19%) had variants of unknown significance. From the patients with the 9 mentioned genes sequenced (424 pts), 14.6% had P/LP variants in MYBPC3, 8.7% MYH7, 4.5% TNNT2, 1.7% TNNI3. Patients were 51 ± 16 years-old, 59% males. Genotype was associated with the following: birthplace (p = 0.005); age (p < 0.001); family history of HCM (p < 0.0005); hypertension (p < 0.0005); chest pain (p = 0.015); pattern of hypertrophy (p = 0.006); left ventricular hypertrophy on the ECG (p < 0.0005); family history of sudden cardiac death (SCD) (p = 0.002). G+ patients more frequently had more than one risk factor for SCD (p = 0.002) and a higher ESC-SCD risk score (p = 0.003). In survival analysis, G+ was associated with SCD (p = 0.017) and MYH7+ with LV systolic dysfunction (p = 0.038). Half of the registry patients had genetic testing. Sarcomere-positive patients had distinct demographics, ECG, imaging characteristics and family history and are at increased risk of SCD. The presence of a MYH7 mutation was associated with evolution towards LV systolic dysfunction. Show less

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease and is often a consequence of mutations in the myosin-binding protein C gene (MYBPC3). Until now, however, no systematic review has been published on mutations of this gene in a Portuguese population. In a Portuguese population of HCM patients: 1) to determine the prevalence of mutations in the MYBPC3 gene; 2) to characterize the mutations genetically; 3) to analyze the phenotype and compare it with the genotype-phenotype correlations for mutations in this gene described in the literature. We studied 45 consecutive index patients with HCM (41 with familial HCM). In each patient, we performed a genetic study to detect mutations in the MYBPC3 gene. Once a mutation was identified and genetically characterized, a broad phenotypic evaluation was performed. The genetic and clinical data were then compared with those described in the literature. Of the 45 patients, 5 (11.1%) showed mutations in the MYBPC3 gene (2 deletions and 3 missense mutations), all in patients with familial HCM. Of these, 4 were 'new' mutations: Ala 522 Thr (exon 17); Gli 1205 Asp (exon 32); Lis 505 Del (exon 17) and Lis 813 Del (exon 25). The other mutation, Arg 502 Gln (exon 17), had been previously described in the literature. Three of the 5 mutations were located in exon 17. Four of these 5 patients were symptomatic, mainly with heart failure and supraventricular arrhythmias. No patient was at high risk for sudden cardiac death. Most of the patients had non-obstructive HCM. The ECG, echocardiogram, Holter monitoring and treadmill exercise test showed highly variable results, reflecting the heterogeneity typical of this disease. In a Portuguese population of 45 HCM patients, 5 (11.1%) had mutations in the MYBPC3 gene (3 missense mutations--theoretically less frequent in the MYBPC3 gene--and 2 deletions). Four of these were 'new' mutations and 3 of them were located in exon 17 (which may be a 'hot spot' for MYBPC3 gene mutations in the Portuguese population). In all the patients, the phenotypic expression was different from that usually described for these mutations; in 3 of our patients, the clinical manifestations and penetrance were of early onset and one patient had a highly symptomatic form of obstructive hypertrophic cardiomyopathy. These data reflect the large number of exceptions to the classic genotype-phenotype correlations in HCM, highlighting the role of other factors, genetic and non-genetic, in regulating penetrance, clinical expression and prognosis in each family and in each individual patient. Show less